W32.Pet_Tick.G

NOTES:
Throughout this writeup:

• \Windows refers to the folder in which Windows is installed, even if the folder has a name other than \Windows.
• \Startup refers to the \Startup folder of the user who was logged on to Windows when the worm was executed.

1. Arrival
This worm arrives as the following email message:

Subject: New Virus Alert !!
Message:
This is a fix against I-Worm.Magistr.
Run the attached file (MSVA.EXE) to detect, repair and protect you against this malicious worm

The email message is designed to appear to be sent by Microsoft, when in fact it has been mailed by the worm.


2. Insertions
This worm inserts the following files on the computer:

• \Windows\Runw32.exe
• \Windows\System\Msva.exe
• \Startup\VARegistered.htm

3. Modifications
The worm may add a line to the Win.ini file as follows:

[windows]
run=%windir%\runw32.exe

4. Infections
A small script is appended to files with .htm* extensions that are in the \Windows folder. The script causes the following message to be displayed:

This file is infected by my new virus
Written by PetiK (c)2001
HTML/W32.MaLoTeYa.Worm

The worm also changes the Internet Explorer home page to the attacker's home page.


5. How the worm works
Activation from locations other than the \Windows folder
When the worm is executed, if it is not located in the \Windows folder, it does the following:

• Inserts itself onto the system
• Modifies the Win.ini file
• Creates the VARegistered.htm file
• Displays the following message:
  

Activation from the \Windows folder
When the worm is executed, if it is located in the \Windows folder, it does the following each time Windows starts (following the initial infection):

• Infects all the .html files in the \Windows folder.
• Sends country information it finds in the Win.ini file to the author, using a mail server located in the United Kingdom.
• Iterates through the cache folder of Internet Explorer and searches for the .htm* files. Each file that is found is searched for lines that contain the mailto: command. The mailto: commands are used to send each recipient an email message that contains a copy of the worm.

6. Payload
On Tuesdays, the worm changes the title bar text of the System Properties window to PetiK always is with you :-).

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary